1. Field of the Invention
This invention relates to concrete piles and more particularly to a tension pile splice.
2. Description of the Prior Art
Concrete piles have many advantages over wood or steel members. However, ordinary steel reinforced concrete is very limited for such use because compression applied to drive a reinforced pile will cause torsion forces which crack and destroy the pile quite easily.
Pre-stressing of beams was suggested early in the 20th Century and has developed rapidly since that time. It was then discovered that pre-stressed piles would confine the damaging tensile wave which is reflected from the pile end after a compression wave, to the limits of the tensile strength of the concrete.
As a consequence, a pre-stressed concrete pile may be driven with many thousands of blows to a refusal of practically zero penetration per blow.
After that development, it became apparent that a substantial improvement in the handling and working capability of the pile could be obtained by making the pile in reasonable length sections and coupling or splicing the piles in the field during the driving operation. A very successful system has been devised for properly coupling such sections in order that the driving force is transmitted through the coupling splice between the piles effectively and efficiently.
Whereas it is normally considered that the forces acting on a pile will be in compression, because that is the purpose of the pile design, nevertheless there are field situations wherein the forces are reversed, or become negative compression, and tend to separate the spice. Obviously separation of a splice during a construction period, for example, could be very disasterous. The prior art has dealt extensively with connectors for compression connections. U.S. Pat. Nos. 1,073,614; 1,838,791; 1,912,111; 3,201,834; 3,422,630; and 3,650,553 are good teaching art in compression structures, and are useful for contrast teaching to the present invention; which has excellent compression capability and novel tension features.
This invention is to be used in conjunction with known pre-stressed pile and compression coupling techniques on structures.
The invention, in particular, relates to the distribution of tensile loading to the body of a pre-stressed concrete pile in such a manner as to distribute loading to a factor below the tensile strength of the concrete.
An object of the invention is to provide a pile coupling which will prevent separation of segments in the event the loading becomes negative for any reason.
Other objects and a fuller understanding of this invention may be had by referring to the summary of the invention, the description and the claims, taken in conjunction with the accompanying drawings.